Researcher:
Taşaltın, Nevin

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Nevin

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Taşaltın

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Taşaltın, Nevin

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2011 - 20125

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    Fabrication of ZnO nanowires and nanorods
    (Elsevier, 2012) Öztürk, Sadullah; Kılınç, Necmettin; Öztürk, Zafer Ziya; Department of Physics; Taşaltın, Nevin; Researcher; Department of Physics; College of Sciences; 220956
    In this study, we focused on the fabrication of two types of ZnO nanostructures, nanorods and nanowires, using different techniques. ZnO nanowires were fabricated by cathodically induced sol-gel electrodeposition using an anodic aluminum oxide (AAO) template. ZnO nanowires were approximately 65 nm in diameter and 10 mu m in length. Also, ZnO nanorods were fabricated by a hydrothermal technique using ZnO seed layer coated glass substrate. ZnO nanorods were approximately 30 nm in diameter and 1 mu m in length. Obtained vertical aligned ZnO nanowires and nanorods were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and UV-vis spectrophotometry.
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    Investigation of the hydrogen gas sensing properties of nanoporous Pd alloy films based on AAO templates
    (Elsevier, 2011) Öztürk, Sadullah; Kılınç, Necmettin; Öztürk, Zafer Ziya; Department of Physics; Taşaltın, Nevin; Researcher; Department of Physics; College of Sciences; 220956
    In this study, the hydrogen sensing properties of nanoporous Pd-Ag and Pd-Cu alloy films based on anodic aluminum oxide (AAO) templates were investigated at various temperatures (25-100 degrees C) and hydrogen with concentrations in the range between 250 and 5000ppm in high purity nitrogen to determine the temperature-sensitivity relationship. A hexagonally shaped AAO template of approximately 50nm in diameter and 10 mu m in length was fabricated as a substrate for supporting a nanoporous Pd alloy film with an approximate thickness of 80 nm. The morphologies of the AAO template and the Pd alloy films were studied by scanning electron microscopy (SEM). The hydrogen sensing properties of the nanoporous Pd-Ag and Pd-Cu alloy films were measured using a transient resistance method. The sensor responses of the nanoporous Pd-Ag and Pd-Cu films on the AAO template were better than the traditional Pd-Ag and Pd-Cu thin film sensors; the sensitivities of the sensors were approximately 1.6% and 1.2%, respectively, for 1000ppm H(2), and the detection limit was 250ppm at room temperature. The highest sensitivity was measured at room temperature for all alloy nanoporous sensors, and the sensitivity of the Pd-Ag nanoporous alloy was higher than that of the Pd-Cu nanoporous alloy.
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    Resonant vibrations of surface-supported microdroplets: an optical spectroscopy study
    (IEEE, 2011) N/A; Department of Physics; N/A; Department of Physics; Department of Physics; Department of Physics; Kiraz, Alper; Karadağ, Yasin; Jonas, Alexandr; Küçükkara, İbrahim; Taşaltın, Nevin; Faculty Member; PhD Student; Other; Other; Researcher; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; College of Sciences; 22542; N/A; N/A; N/A; N/A
    Vibrations of NaCl-water microdroplets deposited on a vertically oscillating superhydrophobic substrate are studied using whispering gallery mode (WGM) optical spectroscopy. By monitoring the WGM width at different oscillation frequencies, lowest-order axisymmetric mechanical resonances are observed in agreement with the theoretical prediction.
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    PublicationOpen Access
    Preparation and characterization of superhydrophobic surfaces based on hexamethyldisilazane-modified nanoporous alumina
    (SpringerOpen, 2011) Şanlı, Deniz; Department of Physics; Taşaltın, Nevin; Kiraz, Alper; Erkey, Can; Jonas, Alexandr; Faculty Member; Faculty Member; Department of Physics; College of Sciences; N/A; 22542; 29633; N/A
    Superhydrophobic nanoporous anodic aluminum oxide (alumina) surfaces were prepared using treatment with vapor-phase hexamethyldisilazane (HMDS). Nanoporous alumina substrates were first made using a two-step anodization process. Subsequently, a repeated modification procedure was employed for efficient incorporation of the terminal methyl groups of HMDS to the alumina surface. Morphology of the surfaces was characterized by scanning electron microscopy, showing hexagonally ordered circular nanopores with approximately 250 nm in diameter and 300 nm of interpore distances. Fourier transform infrared spectroscopy-attenuated total reflectance analysis showed the presence of chemically bound methyl groups on the HMDS-modified nanoporous alumina surfaces. Wetting properties of these surfaces were characterized by measurements of the water contact angle which was found to reach 153.2 ± 2°. The contact angle values on HMDS-modified nanoporous alumina surfaces were found to be significantly larger than the average water contact angle of 82.9 ± 3° on smooth thin film alumina surfaces that underwent the same HMDS modification steps. The difference between the two cases was explained by the Cassie-Baxter theory of rough surface wetting.
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    PublicationOpen Access
    Probing microscopic wetting properties of superhydrophobic surfaces by vibrated micrometer-sized droplets
    (American Chemical Society (ACS), 2011) Karadağ, Yasin; Kücükkara, İbrahim; Department of Physics; Jonas, Alexandr; Kiraz, Alper; Taşaltın, Nevin; Faculty Member; Department of Physics; College of Sciences; N/A; 22542; N/A
    We determine contact angles of micrometer-sized NaCl-water droplets on superhydrophobic surfaces by analyzing their lowest-order axisymmetric vibrational resonances driven by vertical oscillations of the surface. Fluorescence spectra of the dye-doped droplets excited by laser light feature whisperinggallery modes (WGMs) whose spectral widths depend on the droplet vibration amplitude, thus enabling precise measurements of the droplet mechanical resonant frequency. Following droplet size determination byWGM mode-matching, we calculate the contact angles from the dependence of the measured mechanical resonant frequency on the droplet size for two surfaces with different superhydrophobicity levels, and find a good correlation with the values measured by direct imaging of millimeter-sized droplets.